Communication method and system

ABSTRACT

Methods and systems for communicating a message through a communication network are provided. A method for transmitting a message through a communication network may include: partitioning the message into at least two parts; generating at least two bit sequences each of which carries a corresponding part of the message; modulating the at least two bit sequences to form a modulated signal frame which includes at least two modulated parts corresponding to the at least two bit sequences, respectively, where the at least two modulated parts of the modulated signal frame have different power levels; and transmitting the modulated signal frame through the communication network.

TECHNICAL FIELD

The present disclosure generally relates to communication methods andsystems.

BACKGROUND

In modern communication technology, how to alleviate channel congestionis one of the major concerns. In conventional communication methods,transmit data rate control (TDRC) is used to reduce the channel load byapplying a high-order modulation scheme. However, high-order modulationmay lead to low reliability.

SUMMARY

According to one embodiment, a method for transmitting a message througha communication network is provided. The method may include:partitioning the message into at least two parts; generating at leasttwo bit sequences each of which carries a corresponding part of themessage; modulating the at least two bit sequences to form a modulatedsignal frame which includes at least two modulated parts correspondingto the at least two bit sequences, respectively, where the at least twomodulated parts of the modulated signal frame have different powerlevels; and transmitting the modulated signal frame through thecommunication network.

In some embodiments, partitioning the message may include: determiningtype of the message; selecting a partition scheme based on the type ofthe message; and partitioning the message into the at least two partsaccording to the selected partition scheme. In some embodiments, thepartition scheme of the message may be selected based on the type of themessage and a configuration file which lists out various message typesand their corresponding partition schemes.

In some embodiments, the at least two parts of the message may beappended with corresponding at least two parts of header data,respectively, and the at least two parts of the message appended withthe at least two parts of the header data may be encoded to obtain theat least two bit sequences.

In some embodiments, modulating the at least two bit sequences mayinclude: modulating the at least two bit sequences separately to obtainthe at least two modulated parts having different power levels; andcombining the at least two modulated parts into the modulated signalframe. In some embodiments, the at least two bit sequences may bemodulated using an unequal error protection method.

In some embodiments, the communication network is a vehicularcommunication network and the message is a basic safety message (BSM),the at least two bit sequences may include a first bit sequence and asecond bit sequence, the first bit sequence may carry positioninformation, and the at least two modulated parts of the modulatedsignal frame may include a first modulated part corresponding to thefirst bit sequence and a second modulated part corresponding to thesecond bit sequence, where the first modulated part has a power levelhigher than that of the second modulated part.

In some embodiments, transmitting the modulated signal frame through thecommunication network may include: transforming the modulated signalframe from frequency domain into time domain to obtain a time domaindiscrete signal frame; transforming the time domain discrete signalframe into a time domain continuous signal frame; and transmitting thetime domain continuous signal frame at a predetermined frequency.

In some embodiments, the modulated signal frame may carry informationindicating that the modulated signal frame includes at least twomodulated parts corresponding to at least two parts of the message andhaving different power levels.

In some embodiments, the modulated signal frame may carry a physicallayer convergence protocol (PLCP) header in which a “Reserved” field maybe used to indicate whether the modulated signal frame includes at leasttwo modulated parts corresponding to at least two parts of the messageand having different power levels.

In some embodiments, a “RATE” field of the PLCP header may include dataindicating coding rate of the first bit sequence.

According to one embodiment, a method for receiving a message through acommunication network is provided. The message is partitioned into atleast two parts each of which is carried in a corresponding modulatedpart of a first modulated signal frame, and the at least two modulatedparts of the first modulated signal frame have different power levels.The method may include: receiving the first modulated signal frame;obtaining control information of the message from the first modulatedsignal frame; and obtaining the message carried in the first modulatedsignal frame based on the control information, which includes:demodulating and decoding the first modulated signal frame as it onlyhas one modulated part to obtain a first part of the message; encodingand modulating the first part of the message to obtain a secondmodulated signal frame; demodulating and decoding a third modulatedsignal frame which is a difference between the first modulated signalframe and the second modulated signal frame, as the third modulatedsignal frame has only one modulated part, to obtain a second part of themessage; and repeating the above processes for a corresponding number oftimes until all the at least two parts of the message are obtained,where the corresponding number may be determined based on the controlinformation.

In some embodiments, the control information may include the number ofthe at least two parts of the message, types of data respectivelycontained in the at least two parts of the message, power levelsrespectively corresponding to the at least two parts of the message, andthe like.

In some embodiments, the method may further include: determining whethereach of the obtained at least two parts of the message has an error; ifnone of the obtained at least two parts of the message is determined tohave an error, combining the obtained at least two parts of the messagebased on the control information; and transmitting a combination resultto an application layer. In some embodiments, if one of the at least twoparts of the message is determined to have an error, the rest part ofthe message which is determined to have no error may be transmitted tothe application layer. Based on the control information, type of datatransmitted to the application message may be recognized.

In some embodiments, the communication network is a vehicularcommunication network, the control information of the message may beobtained based on information in a physical layer convergence protocol(PLCP) header which may be partially carried in a “SIGNAL” part of thefirst modulated signal frame.

In some embodiments, the control information of the message may beobtained based on type of the message and a configuration file listingout various message types and their corresponding control information.

In some embodiments, the method may further include: determining whetherthe message is partitioned into at least two parts based on a “Reserved”field of the PLCP header; and if yes, performing the above describedprocesses to obtain the at least two parts of the message.

In some embodiments, the third modulated signal frame may be obtainedbased on vector subtraction between the first modulated signal frame andthe second modulated signal frame.

According to one embodiment, a system for transmitting a message througha communication network is provided. The system may include: a processorfor partitioning the message into at least two parts and generating atleast two bit sequences each of which carries a corresponding part ofthe message; a modulator for modulating the at least two bit sequencesto form a modulated signal frame which includes at least two modulatedparts corresponding to the at least two bit sequences, respectively,where the at least two modulated parts of the modulated signal framehave different power levels; and a transmitter for transmitting themodulated signal frame through the communication network.

In some embodiments, the processor may be configured to: determine typeof the message; select a partition scheme based on the type of themessage; partition the message according to the selected partitionscheme to obtain the at least two parts of the message; and control anencoder to encode the at least two parts of the message to obtain the atleast two bit sequences. In some embodiments, the processor may beconfigured to select the partition scheme based on the type of themessage and a configuration file which lists out various message typesand their corresponding partition schemes.

In some embodiments, the processor may be configured to: append the atleast two parts of the message with corresponding at least two parts ofheader data, respectively; and control an encoder to encode the at leasttwo parts of the message appended with the at least two parts of theheader data to obtain the at least two bit sequences.

In some embodiments, the modulator may be configured to: modulate the atleast two bit sequences separately to obtain the at least two modulatedparts having different power levels; and combine the at least twomodulated parts into the modulated signal frame. In some embodiments,the modulator may be configured to modulate the at least two bitsequences using an unequal error protection method.

In some embodiments, the communication network is a vehicularcommunication network and the message is a basic safety message, theprocessor may be configured to generate the at least two bit sequencesto include a first bit sequence and a second bit sequence, where thefirst bit sequence may carry position information, the at least twomodulated parts of the modulated signal frame may include a firstmodulated part corresponding to the first bit sequence and a secondmodulated part corresponding to the second bit sequence, where the firstmodulated part has a power level higher than that of the secondmodulated part.

In some embodiments, the modulator may be configured to transform themodulated signal frame from frequency domain into time domain to obtaina time domain discrete signal frame and transform the time domaindiscrete signal frame into a time domain continuous signal frame; andthe transmitter may be configured to transmit the time domain continuoussignal frame at a predetermined frequency.

In some embodiment, the modulated signal frame may carry informationindicating that the modulated signal frame includes at least twomodulated parts having different power levels.

In some embodiments, the modulated signal frame may carry a physicallayer convergence protocol (PLCP) header in which a “Reserved” field maybe used to indicate whether the message the modulated signal frameincludes at least two modulated parts having different power levels.

In some embodiments, a “RATE” field of the PLCP header may includeinformation indicating coding rate of the first bit sequence.

According to one embodiment, a system for receiving a message through acommunication network is provided. The message is partitioned into atleast two parts each of which is carried in a corresponding modulatedpart of a first modulated signal frame, and the at least two modulatedparts of the first modulated signal frame have different power levels.The system may include a receiver for receiving the first modulatedsignal frame carrying the message through the communication network. Thesystem further includes a processor configured to: obtain controlinformation of the message from the first modulated signal framereceived by the receiver; and control obtaining the message carried inthe first modulated signal frame based on the control information, whichmay include: controlling a demodulator and a decoder to demodulate anddecode the first modulated signal frame as it only has one modulatedpart to obtain a first part of the message; controlling an encoder and amodulator to encode and modulate the first part of the message to obtaina second modulated signal frame; controlling the demodulator and thedecoder to demodulate and decode a third modulated signal frame which isa difference between the first modulated signal frame and the secondmodulated signal frame, as the third modulated signal frame has only onemodulated part, to obtain a second part of the message; and controllingthe demodulator, the decoder, the encoder and the modulator to repeatthe above processes for a corresponding number of times until all the atleast two parts of the message are obtained, where the correspondingnumber may be determined based on the control information.

In some embodiments, the control information may include the number ofthe at least two parts of the message, types of data respectivelycontained in the at least two parts of the message, power levelsrespectively corresponding to the at least two parts of the message, andthe like.

In some embodiments, the processor may be further configured to:determine whether each of the obtained at least two parts of the messagehas an error; if none of the obtained at least two parts of the messageis determined to have an error, combine the obtained at least two partsof the message based on the control information; and transmit acombination result to an application layer. In some embodiments, theprocessor may be configured to: if one of the at least two parts of themessage is determined to have an error, transmit the rest part of themessage which is determined to have no error to the application layer.

In some embodiments, the communication network is a vehicularcommunication network, the processor may be configured to obtain thecontrol information of the message based on a physical layer convergenceprotocol (PLCP) header which may be partially carried in a “SIGNAL” partof the first modulated signal frame.

In some embodiments, the processor may be configured to obtain thecontrol information of the message based on message type informationcontained in the PLCP header and a configuration file listing outvarious message types and their corresponding control information.

In some embodiments, the processor may be configured to determinewhether the message is partitioned into at least two parts based on a“Reserved” field of the PLCP header; and if yes, perform the abovedescribed processes to obtain the at least two parts of the message.

In some embodiments, the processor may be configured to obtain the thirdmodulated signal frame based on vector subtraction between the firstmodulated signal frame and the second modulated signal frame.

In one embodiment, a method for extracting a message from a receivedsignal frame is provided. The method may include: receiving a signalframe having N parts which are modulated with different power levels,where N is an integer equal to or greater than 2; demodulating anddecoding the received signal frame to obtain N bit sequences whichcorrespond to the N parts respectively; and forming a message based onthe N bit sequences and a partition scheme according to which themessage is partitioned into N message parts corresponding to the N bitsequences respectively.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing and other features of the present disclosure will becomemore fully apparent from the following description and appended claims,taken in conjunction with the accompanying drawings. Understanding thatthese drawings depict only several embodiments in accordance with thedisclosure and are, therefore, not to be considered limiting of itsscope, the disclosure will be described with additional specificity anddetail through use of the accompanying drawings.

FIG. 1 schematically illustrates a flow chart of a method forcommunicating a safety message through a vehicular communication networkaccording to one embodiment;

FIG. 2 illustrates contents in a basic safety message (BSM);

FIG. 3 illustrates a first subpart of the BSM according to oneembodiment;

FIG. 4 illustrates a second subpart of the BSM according to oneembodiment;

FIG. 5 illustrates an original structure of a PLCP header according toIEEE 802.11p;

FIG. 6 illustrates a redefined PLCP header according to one embodiment;

FIG. 7 schematically illustrates superposition coding of two QPSKmodulation constellations;

FIG. 8 schematically illustrates a block diagram of a system 300 fortransmitting a message through a communication network; and

FIG. 9 schematically illustrates a block diagram of a system 400 forreceiving a message through a communication network.

DETAILED DESCRIPTION

In the following detailed description, reference is made to theaccompanying drawings, which form a part hereof. In the drawings,similar symbols typically identify similar components, unless contextdictates otherwise. The illustrative embodiments described in thedetailed description, drawings, and claims are not meant to be limiting.Other embodiments may be utilized, and other changes may be made,without departing from the spirit or scope of the subject matterpresented here. It will be readily understood that the aspects of thepresent disclosure, as generally described herein, and illustrated inthe Figures, can be arranged, substituted, combined, and designed in awide variety of different configurations, all of which are explicitlycontemplated and make part of this disclosure.

Conventional communication methods may use transmit data rate control(TDRC) modulation schemes at a transmitter side to reduce channel load.However, reliability of these communication methods may be affectedbecause signal frames obtained from modulations with a high data ratemay be easily affected by noise and interference, especially forreceivers far away from the transmitter. Inventors found that, bymodulating different parts of a message with different power levelsbased on importance of these parts, not only the transmission durationof the message may be reduced, but also at least the relativelyimportant part of this message can be received easier.

Communication of a vehicle safety message through a communicationnetwork according to embodiments will be illustrated in detailhereunder. The vehicle safety message may be a basic safety message(BSM), cooperative awareness message (CAM) or decentralizedenvironmental notification message (DENM), which is communicated througha vehicular communication network. Extensions to communicating othermessages through other communication networks may be easily conceived inlight of this disclosure.

FIG. 1 schematically illustrates a flow chart of a method 100 forcommunicating a safety message through a vehicular communication networkaccording to one embodiment. Referring to FIG. 1, in S101, generating afirst bit sequence containing a safety message.

Medium access mechanism in wireless access in vehicular environments(WAVE) is defined as a commonly assumed physical layer communicationmechanism based on IEEE 802.11p. According to the communicationmechanism, data included in the safety message, e.g., global positioningsystem (GPS) data, sensor data, and the like, may be generated fromapplications in an application layer. Thereafter, the safety messagedata may be contained in a WAVE short message (WSM) data field andappended with headers in a WAVE short message protocol (WSMP) layer. Thesafety message appended with the WSMP headers may be then transmitteddownwardly to lower layers, such as a logical link control (LLC) layer,a medium access control (MAC) layer, and the like, and appended withother headers in the lower layers. Such that, a bit sequence carryingthe safety message, i.e., the first bit sequence, may be generated.

In S103, partitioning the first bit sequence carrying the safety messageinto a second bit sequence and a third bit sequence.

Each one of the second and third bit sequences may include a part of thesafety message. Therefore, different contents of the safety message withdifferent importance may be partitioned into different bit sequences. Insome embodiments, the first bit sequence may be partitioned into morethan two groups, and each of the groups may include a corresponding partof the safety message.

Different types of messages may be partitioned using different partitionschemes. In some embodiments, a unit embedded at bottom of the MAC layermay be configured to partition the first bit sequence. Specifically, theunit may be configured to: determine type of the safety message; selecta partition scheme based on the type of the safety message and aconfiguration file which lists out various safety message types andtheir corresponding partition schemes; and partition the safety messageaccording to the selected partition scheme to obtain the second bitsequence and the third bit sequence.

In some embodiments, the first bit sequence may include a data fieldindicating the message type, such that the message type can bedetermined based on a value of such data field. In such ways, themessage type may be determined, for example, the safety messagecontained in the first bit sequence may be determined to be a BSM.

Thereafter, the partition scheme may be selected based on the identifiedmessage type. In some embodiments, a configuration file listing out aplurality of partition schemes corresponding to various message typesrespectively may be stored in the unit. By reading the configurationfile, how to partition the first bit sequence may be determined based onthe type of the safety message carried in the first bit sequence.

Hereunder gives an example of partitioning a BSM. FIG. 2 illustratescontents in a BSM. It could be seen from FIG. 2 that the BSM may includeposition data which are most essential for collision avoidanceapplications. Other data in the BSM, such as speed, heading,acceleration, brake state and size, may be less important. Accordingly,in some embodiments, if the safety message is determined to be a BSM,contents including the position data, as illustrated in FIG. 3, may begrouped as a first part of the BSM; and the rest contents, asillustrated in FIG. 4, may be grouped as a second part of the BSM. Insome embodiments, the partition scheme for the BSM may be altered, forexample, speed, heading and acceleration data may be grouped into thefirst part together with the position data.

The configuration file may be parameterized, which means the partitionschemes corresponding to the message types may be adjusted based onpractical requirements. Besides, the configuration file can be updatedto include other partition schemes for new message types.

As stated above, the first bit sequence may include header data, such asWSMP headers, LLC headers and/or MAC headers. Regarding the header data,there may be several solutions to partition them. In some embodiments,the header data may be grouped into either the first bit sequence or thesecond bit sequence. In some embodiments, the header data may bepartitioned into two portions, where the first portion of the headerdata may include relatively important data and may be grouped into thefirst bit sequence with the first part of the safety message which maycontain more important contents, and the second portion of the headerdata may include relatively less important data and may be grouped intothe second bit sequence with the less important second part of thesafety message.

Based on the partition scheme, the first bit sequence may be partitionedto obtain the second and third bit sequences. In subsequent modulations,the second and third bit sequences may need to have the same length.Therefore, in some embodiments, if the second and third bit sequences donot have the same length, pad bits may be added to the shorter one ofthe second and third bit sequences to make them have the same length.However, adding pad bits may be optional, since an identical length ofthe second and third bit sequences may be achieved using differentencoding rates.

In some embodiments, the unit may be embedded in another layer higherthan the MAC layer. However, if the first bit sequence is partitioned inthe MAC layer, the partition scheme may cover more header data appendedto the safety message.

In S105, generating a physical layer convergence protocol (PLCP) header,and appending each of the second and third bit sequences with a“SERVICE” field of the PLCP header.

A signal frame to be transmitted may carry the message together withsome basic information of the message, such that a receiver maydemodulate and decode the signal frame to obtain the message based onthe basic information. In vehicular communications, according to IEEE802.11p, the basic information may be contained in a PLCP header.Specifically, a “SERVICE” field of the PLCP header may be encoded andmodulated with the message to form a “DATA” part of a modulated signalframe, while other data fields of the PLCP header may be encoded andmodulated to form a “SIGNAL” part of the modulated signal frame.

The PLCP header generated in S105 may indicate that the safety messageis partitioned and different power levels are allocated to differentparts of the safety message, such that receivers may use suitabledemodulation and/or decoding schemes accordingly. Therefore, in someembodiments, spare bits in the PLCP header may be used to indicate thisinformation.

FIG. 5 illustrates an original structure of a PLCP header according toIEEE 802.11p. FIG. 6 illustrates a redefined PLCP header according toone embodiment. Referring to FIGS. 5 and 6, a 1-bit “Reserved” field,which is originally default, may be utilized as a “SWITCH” identifierfor indicating whether the safety message is partitioned. For example,the 1-bit in the “Reserved” field may be assigned to be “0” according toIEEE 802.11p, once the 1-bit in the “Reserved” field turns to be “1”, itmay mean that the “Reserved” field has been used as a “SWITCH”identifier indicating that the safety message is partitioned. A receivermay select a suitable way to demodulate and decode based on the “SWITCH”identifier.

Furthermore, some redefinitions of the PLCP header may be implemented.For example, a “RATE” field should originally, according to IEEE802.11p, represent the coding rate of data appended with the “RATE”field. In some embodiments, the “RATE” field in the redefined PLCPheader may represent a coding rate of the second bit sequence. Sincedifferent coding rates may be used for the second and third bitsequences, in some embodiments, the “SERVICE” field may include dataindicating a coding rate of the third bit sequence.

At receiver side, data in the “SIGNAL” part may be obtained before datain the “DATA” part is obtained, such that the basic informationcontained in the PLCP header, especially the coding rate, payload lengthof the “DATA” part, can be obtained. After demodulating and decoding the“DATA” part based on the basic information to obtain the second bitsequence and the “SERVICE” field, the coding rate of the third bitsequence contained in the “SERVICE” field may be known. Thereafter,demodulation and decoding may be performed to obtain the third bitsequence.

In S107, encoding the second and third bit sequences which arerespectively appended with the “SERVICE” fields.

According to IEEE 802.11p, there are several encoding schemes withdifferent encoding rates can be selected. Through a proper forward errorcorrection (FEC) encoder with different coding rates, the lengths of theencoded second and third bit sequences may be adjusted to be equal toeach other, even if the second and third bit sequences do not have thesame length before they are encoded.

In S109, modulating the encoded second and third bit sequences to obtaina first symbol sequence.

The symbol sequence may include a first modulated part corresponding tothe encoded second bit sequence and a second modulated partcorresponding to the encoded third bit sequence. Besides, the firstmodulated part may have a power level greater than that of the secondmodulated part.

Allocating different powers to the first and second modulated parts mayensure that the first modulated part carrying the more important part ofthe safety message and more important portion of the header data can bedemodulated and decoded more easily. There may be several practicalschemes for modulating the encoded second and third bit sequences. Insome embodiments, the encoded second and third bit sequences may beseparately modulated to obtain the first and second modulated partshaving different power levels. For example, using an unequal errorprotection (UEP) method, the first and second modulated parts can beallocated with different powers. Thereafter, the first and secondmodulated parts may be combined to form the first symbol sequence. Insome embodiments, the first and second modulated parts may be combinedusing superposition coding. In some embodiments, the encoded second andthird bit sequences may be modulated using a scalable modulation, suchthat the first symbol sequence may include the first and secondmodulated parts having different power levels. Detail information of theabove described schemes may be obtained by referring to “SuperpositionCoding in the Downlink of CDMA Cellular Systems” (written by S. Boppinget al., and published in “Wireless Communications and NetworkingConference, 2006”), “Optimizing the Energy of Different Bitstreams ofTurbo Code” (written by J. Hokfelt et al., and published in “TurboCoding Seminar Proc., pp 59-63, 1996”), and “Scalable Modulation forScalable Wireless Videocast” (written by L. Cai et al., and published in“INFOCOM, 2010 Proceedings IEEE”).

Hereunder gives a specific example for illustrating modulation with UEP,in which superposition coding of quadrature phase shift keying (QPSK)modulation constellations is used. Other modulation constellations andother UEP schemes could be also applied in the similar way as follows.

FIG. 7 schematically illustrates superposition coding of two QPSKmodulation constellations. Referring to FIG. 7, two bits in the encodedsecond bit sequence may be mapped into a first QPSK modulationconstellation to obtain a first symbol x₁, while two bits in the encodedthird bit sequence may be mapped into a second QPSK modulationconstellation to obtain a second symbol x₂. Vector superposition may beperformed on x₁ and x₂ to obtain a high-order symbol x. Since x₁,representing more important contents, may be allocated with higherpower, while x₂, representing less important contents, may be allocatedwith lower power, the combined high-order symbol x may be much closer tothe first symbol x₁ than to the second symbol x₂. It could be understoodthat the first symbol x₁ is more likely to be demodulated and decoded atthe receiver side, thus it may have a higher possibility to obtain thetwo bits corresponding to the first symbol x₁. Allocating distinct powerto different bit sequences may be simply achieved by adjusting a powertransfer distribution factor (PTDF) “α”, where the power allocated tothe encoded second bit sequence may be α*P, the power allocated to theencoded third bit sequence may be (1−α)*P, and a is greater than 0.5.Other bits in the encoded second and third bit sequences may bemodulated in the same way, so that a symbol sequence, i.e., the firstsymbol sequence, may be generated.

The first symbol sequence may constitute a “DATA” part of a signal frameto be transmitted.

In S111, generating a second symbol sequence carrying the PLCP headerother than the “SERVICE” field.

According to IEEE 802.11p, a modulation scheme for the PLCP header otherthan the “SERVICE” field is fixed. Using that scheme, the second symbolsequence, which constitutes a “SIGNAL” part of the signal frame to betransmitted, is formed.

In S113, transforming the first symbol sequence and the second symbolsequence into a modulated signal frame.

In some embodiments, the first symbol sequence and the second symbolsequence may be subjected to orthogonal frequency division multiplexing(OFDM) modulation followed by digital-to-analogue conversion, which iswell known in the art. Such that, the first symbol sequence and thesecond symbol sequence may be transformed from frequency domain intotime domain to obtain a time domain discrete signal frame, and the timedomain discrete signal frame may be transformed into a time domaincontinuous signal frame.

In S115, transmitting the modulated signal frame through thecommunication network.

A transmitter may be controlled to transmit the time domain continuoussignal frame at a predetermined frequency through the vehicularcommunication network.

S101 to S115 may be performed in a vehicle. Then the modulated signalframe may be received by another vehicle.

In S201, receiving the modulated signal frame through the communicationnetwork.

Receiving the signal may be implemented by a receiver in a physicallayer of a receiver. Theoretically, all neighboring vehicles within thetransmission range may receive the signal. However, in practice, signaltransmission may be blocked by obstacles. Besides, the receivedmodulated signal frame may be corrupted by noise and interference.

In S203, demodulating and decoding a part of the modulated signal frameto obtain the PLCP header other than the “SERVICE” field.

As stated above, the “SIGNAL” part of the modulated signal frame may bepreferentially demodulated and decoded to obtain the control informationcontained in the PLCP header. Multiple iterations may be performed toensure correct decoding of the second part.

It should be noted that, after the modulated signal frame is received,analogue-to-digital conversion, synchronization, fast Fourier transform,and the like may be performed to transform the received modulated signalframe, which may be a time domain continuous signal frame, into thefirst symbol sequence and the second symbol sequence. Such that, thesecond symbol sequence, i.e., the “SIGNAL” part, may be demodulated anddecoded to obtain information in the PLCP header.

In S205, obtaining control information of the message based on the PLCPheader.

In some embodiments, the control information may include the number ofparts of the message, types of data respectively contained in the atleast two parts of the message, power levels respectively correspondingto the at least two parts of the message, and the like. Based on thecontrol information, the data carried in the modulated signal frame maybe obtained, recognized and used at the receiver side.

In some embodiments, a configuration file may be established in thephysical layer, which lists out various message types and theircorresponding control information. Since the message type may beobtained based on the PLCP header, the corresponding control informationmay also be obtained.

In some embodiments, the control information may further include anidentifier indicating whether the message has been partitioned at thetransmitter side. In some embodiments, the bit in the “Reserved” fieldof the decoded first PLCP header may be used as the identifier. Forexample, if the bit in the “Reserved” field of the decoded first PLCPheader is “1”, it may be determined that the message has beenpartitioned. If yes, then goes to S207; if no, the rest part of themodulated signal frame, i.e., the first symbol sequence, may bedemodulated and decoded as normal.

In S207, performing successive interference cancellation (SIC) to therest part of the modulated signal frame, where each result from the SICprocess is taken as including a part of the message.

Each result from the SIC process is taken as including a part of themessage. SIC is commonly used in the art to demodulate and decode asignal when superposition coding is applied during generation of thesignal. Specifically, the first symbol sequence may be demodulated anddecoded based on the coding rate information in the “RATE” field of thedecoded PLCP header. As stated above, symbols in the first symbolsequence may be closer to symbols corresponding to the encoded secondbit sequence containing more important contents than to symbolscorresponding to the encoded third bit sequence containing lessimportant contents. Therefore, normally the second bit sequence could beobtained more easily. If the decoded second bit sequence includes anerror according to a FCS check result, which means the modulated signalframe may be heavily corrupted, the whole received information may bediscarded. If the decoded second bit sequence doesn't include an erroraccording to the FCS check result, the decoded second bit sequencetogether with the decoded “SERVICE” part may be encoded and modulatedagain as a same way at the transmitter side to obtain a third symbolsequence. Thereafter the third symbol sequence may be removed from thefirst symbol sequence using vector subtraction to obtain a fourth symbolsequence. As described above, the first symbol sequence may be obtainedby combining symbols represents the encoded second and third bitsequences using vector superposition. Therefore, the third bit sequencemay be obtained by demodulating and decoding the fourth symbol sequence.

If the decoded third bit sequence also passes the FCS check, which meansboth the first part of the message carried in the second bit sequenceand the second part of the message carried in the third bit sequence arereceived, both the decoded second bit sequence and the decoded third bitsequence may be used in an application layer for further analyzing. Insome embodiments, the obtained bit sequences containing the parts of themessage may be combined based on the control information of the messageto obtain the complete first bit sequence, and the first bit sequencemay be transmitted to the application layer. If the decoded third bitsequence fails the FCS check, only the decoded second bit sequence maybe transmitted to the application layer. The data transmitted to theapplication layer can be recognized based on the control information.

In some embodiments, the message may be partitioned into more than twoparts, where the number of the parts is known based on the controlinformation. In such scenario, the above processes in S207 may berepeated until all the parts of the message are obtained. For example,if the control information indicates that the message has beenpartitioned into N parts, the above processes may be repeated foranother (N−2) times.

By applying the method 100, transmission efficiency may be increased ashigh-order modulation is applied, while at least transmissionreliability of the first bit group including more important informationmay be improved.

According to one embodiment, a system 300 for transmitting a messagethrough a communication network is provided. The system 300 may be at atransmitter side. FIG. 8 schematically illustrates a block diagram ofthe system 300.

Referring to FIG. 8, the system 300 may include a partition unit 301 forpartitioning the message into at least two parts and generating at leasttwo bit sequences each of which carries a corresponding part of themessage. The partition unit 301 may be embedded in a MAC layer of thetransmitter and may partition the message based on pre-stored partitionschemes respectively corresponding to various types of messages. In someembodiments, the partition unit 301 may append the at least two parts ofthe message with different header data of different importance,respectively, to generate the at least two bit sequences. In someembodiments, the message may be a vehicle safety message communicated ina vehicular communication network, the partition unit 301 may generate aPLCP header which may contain information indicating that the message ispartitioned and different power levels are allocated to different partsof the message during modulation. A “SERVICE” field of the PLCP headermay be inserted to each of the at least two bit sequences. In someembodiments, the partition unit 301 may add padding to the at least twoparts of the message appended with header data, such that the at leasttwo bit sequences may have the same length. Thereafter, the at least twobit sequences and the rest part of the PLCP header may be encoded.

The system 300 may include an encoder 303, such as a FEC encoder, or thelike. The encoder 303 may encode the at least two bit sequences and therest part of the PLCP header, respectively. In some embodiments, theencoder 303 may be configured to encode the at least two parts of themessage appended header data using different coding rates, such that theat least two bit sequences may have the same length.

Detail configurations of the partition unit 301 and the encoder 303 maybe obtained by referring to above descriptions for S101 to S107.

The system 300 may include a modulator for modulating the at least twobit sequences to form a modulated signal frame. The modulated signalframe may include at least two modulated parts corresponding to the atleast two bit sequences, respectively, where the at least two modulatedparts of the modulated signal frame have different power levels. In someembodiments, the modulator may include a mapper 305 for mapping the atleast two bit sequences into constellations with different power levelsto obtain the at least two modulated parts having different powerlevels, and the modulator may further include a superposition coder 307for combining the at least two bit sequences to form the modulatedsignal frame. In some embodiments, the modulator may apply othermodulation mechanism, such as a UEP method, for modulating the at leasttwo bit sequences. In some embodiments, the modulator may furtherinclude an inverse fast Fourier transformer (IFFT) 309 and adigital-to-analogue converter (DAC) 311 to transform the modulatedsignal frame into a time domain continuous signal frame. Detainconfigurations of the modulator may be obtained by referring to abovedescriptions for S109 and S113.

The system 300 may include a radio 313 for transmitting the modulatedsignal frame through the communication network. In some embodiments, theradio 313 may be configured to transmit the time domain continuoussignal frame at a predetermined frequency.

According to one embodiment, a system 400 for receiving a messagethrough a communication network is provided. The system 400 may be at areceiver side. FIG. 9 schematically illustrates a block diagram of thesystem 400.

Referring to FIG. 9, the system 400 may include a radio 401 forreceiving a first modulated signal frame carrying the message throughthe communication network from a transmitter through the communicationnetwork. The message may have been partitioned into at least two partseach of which is carried in a corresponding modulated part of a firstmodulated signal frame, and the at least two modulated parts of thefirst modulated signal frame may have different power levels. Then thereceived first modulated signal frame may go to a analogue-to-digitalconvertor (ADC) 403, a synchronizer 405, a fast Fourier transformer(FFT) 407, a channel estimator 409, etc, for certain processing, suchthat a first symbol sequence carrying the message may be obtained. Aboveprocessing is well known in the art and will not be illustrated indetail here.

The system 400 may include a PLCP decoder 411 for obtaining controlinformation of the message, which may normally be contained in a PLCPheader carried in a part of the first symbol sequence. In someembodiments, the control information may include the number of the atleast two parts of the message, types of data respectively contained inthe at least two parts of the message, power levels respectivelycorresponding to the at least two parts of the message, and the like.After obtaining the control information, whether the message ispartitioned and different parts of the partitioned message are carriedin different modulated parts of the first modulated signal frame havingdifferent power levels may be determined based on the controlinformation.

If the determination is “no”, following demodulation and decodingprocesses may be implemented according to corresponding standards, forexample, according to IEEE 802.11p if the message is a vehicle safetymessage communicated in a vehicular communication network. If thedetermination is “yes”, the rest part of the first symbol sequencecarrying the message may be processed as follows.

Specifically, the system 400 may include a demapper 413 and a decoder415 for demodulating and decoding the rest part of the first symbolsequence as it only has one modulated part. As stated above, the messageis partitioned into at least two parts, and the at least two parts ofthe message are carried in at least two modulated parts having differentpower levels. It could be understood that the rest part of the firstsymbol sequence may be close to a modulated part with a higher powerlevel. Therefore, a first result obtained from the decoder 415 maycorrespond to a first part of the message carried in the modulated partwith the higher power level. Normally, the first part of the message maycontain more important contents of the message, such that at least themore important contents of the message may be obtained better andeasier.

Thereafter, the first result may be encoded and modulated by an encoder417 and a mapper 419 to obtain a second symbol sequence. Using asuccessive interference cancellation (SIC) unit 421, a third symbolsequence which is a difference between the rest part of the first symbolsequence and the second symbol sequence may be obtained, whichdifference may correspond to a second part of the message. Thereafter,the third symbol sequence may be demodulated and decoded by the demapper413 and the decoder 415 to obtain a second result corresponding to thesecond part of the message.

Processing of the demapper 413, the decoder 415, the encoder 417, themapper 419 and the SIC unit 421 may be recycled until all parts of themessage are obtained.

The system 400 may further include a unit (not illustrated in FIG. 9)for extracting information from the obtained results based on apartition scheme according to which the message is partitioned. Theextracted information may be used by other components of the receiverfor further processing.

Detail configurations of components in the system 400 may be obtained byreferring to above descriptions for S201 and S207.

There is little distinction left between hardware and softwareimplementations of aspects of systems; the use of hardware or softwareis generally a design choice representing cost vs. efficiency tradeoffs.For example, if an implementer determines that speed and accuracy areparamount, the implementer may opt for a mainly hardware and/or firmwarevehicle; if flexibility is paramount, the implementer may opt for amainly software implementation; or, yet again alternatively, theimplementer may opt for some combination of hardware, software, and/orfirmware.

While various aspects and embodiments have been disclosed herein, otheraspects and embodiments will be apparent to those skilled in the art.The various aspects and embodiments disclosed herein are for purposes ofillustration and are not intended to be limiting, with the true scopeand spirit being indicated by the following claims.

1. A method for transmitting a message through a communication network,comprising: partitioning the message into at least two parts; generatingat least two bit sequences, wherein each bit sequence carries acorresponding part of the message modulating the at least two bitsequences to form a modulated signal frame that comprises at least twomodulated parts corresponding to the at least two bit sequences,respectively, where the at least two modulated parts of the modulatedsignal frame have different power levels; and transmitting the modulatedsignal frame through the communication network.
 2. The method accordingto claim 1, wherein partitioning the message comprises: determining atype associated with of the message; selecting a partition scheme basedon the type associated with the message; and partitioning the messageaccording to the selected partition scheme to obtain the at least twoparts of the message.
 3. The method according to claim 1, wherein the atleast two parts of the message are appended with corresponding at leasttwo parts of header data, respectively, and the at least two parts ofthe message appended with the at least two parts of the header data areencoded to obtain the at least two bit sequences.
 4. The methodaccording to claim 1, wherein modulating the at least two bit sequencescomprises: modulating the at least two bit sequences separately toobtain the at least two modulated parts having different power levels;and combining the at least two modulated parts into the modulated signalframe.
 5. The method according to claim 1, wherein the communicationnetwork is a vehicular communication network and the message is a basicsafety message, the at least two bit sequences comprise a first bitsequence and a second bit sequence, the first bit sequence carriesposition information, and the at least two modulated parts of themodulated signal frame comprise a first modulated part corresponding tothe first bit sequence and a second modulated part corresponding to thesecond bit sequence, where the first modulated part has a power levelhigher than the power level of the second modulated part.
 6. The methodaccording to claim 1, wherein the modulated signal frame carriesinformation indicating that the modulated signal frame comprises atleast two modulated parts corresponding to at least two parts of themessage and having different power levels.
 7. A method for receiving amessage through a communication network, where the message ispartitioned into at least two parts, wherein each part is carried in acorresponding modulated part of a first modulated signal frame, and theat least two modulated parts of the first modulated signal frame havedifferent power levels, the method comprising: receiving the firstmodulated signal frame; obtaining control information for the messagefrom the first modulated signal frame; and obtaining the message carriedin the first modulated signal frame based on the control information by:demodulating and decoding the first modulated signal frame to obtain afirst part of the message; encoding and modulating the first part of themessage to obtain a second modulated signal frame; demodulating anddecoding a third modulated signal frame, wherein the third modulatedsignal frame comprises a difference between the first modulated signalframe and the second modulated signal frame, to obtain a second part ofthe message; and repeating the steps of demodulating and decoding,encoding and modulating, and demodulating and decoding a number of timesbased on the control information.
 8. The method according to claim 7,further comprising: determining whether each part included in the atleast two parts of the message has an error; if none of the parts of themessage is determined to have an error, combining the at least two partsof the message based on the control information to produce a combinationresult; and transmitting the combination result to an application layer.9. The method according to claim 7, wherein the control information forthe message is obtained based on a type associated with the message anda configuration file listing-Gut various message types and controlinformation corresponding to the various message types.
 10. A system fortransmitting a message through a communication network, comprising: aprocessor for partitioning the message into at least two parts andgenerating at least two bit sequences, wherein each bit sequence carriesa corresponding part of the message; a modulator for modulating the atleast two bit sequences to form a modulated signal frame that comprisesat least two modulated parts corresponding to the at least two bitsequences, respectively, where the at least two modulated parts of themodulated signal frame have different power levels; and a transmitterfor transmitting the modulated signal frame through the communicationnetwork.
 11. The system according to claim 10, wherein the processor isconfigured to: determine a type associated with the message; select apartition scheme based on the type associated with the message; andpartition the message according to the selected partition scheme toobtain the at least two parts of the message.
 12. The system accordingto claim 10, wherein the modulator is configured to: modulate the atleast two bit sequences separately to obtain the at least two modulatedparts having different power levels; and combine the at least twomodulated parts into the modulated signal frame.
 13. The systemaccording to claim 12, wherein the modulator is configured to: appendthe at least two parts of the message with corresponding at least twoparts of header data, respectively; and control an encoder to encode theat least two parts of the message appended with the at least two partsof the header data to obtain the at least two bit sequences.
 14. Thesystem according to claim 10, wherein the communication network is avehicular communication network and the message is a basic safetymessage, the processor is configured to generate the at least two bitsequences to comprise a first bit sequence and a second bit sequence,where the first bit sequence carries position information, and the atleast two modulated parts of the modulated signal frame comprise a firstmodulated part corresponding to the first bit sequence and a secondmodulated part corresponding to the second bit sequence, where the firstmodulated part has a power level higher than the power level of thesecond modulated part.
 15. The system according to claim 10, wherein themodulated signal frame carries information indicating that the modulatedsignal frame comprises at least two modulated parts corresponding to atleast two parts of the message and having different power levels.
 16. Asystem for receiving a message through a communication network, wherethe message is partitioned into at least two parts, wherein each part iscarried in a corresponding modulated part of a first modulated signalframe, and the at least two modulated parts of the first modulatedsignal frame have different power levels, the system comprising areceiver for receiving a first modulated signal frame carrying themessage through the communication network, and a processor that isconfigured to: obtain control information for the message from the firstmodulated signal frame received by the receiver; and control obtainingthe message carried in the first modulated signal frame based on thecontrol information by: controlling a demodulator and a decoder todemodulate and decode the first modulated signal frame to obtain a firstpart of the message; controlling an encoder and a modulator to encodeand modulate the first part of the message to obtain a second modulatedsignal frame; controlling the demodulator and the decoder to demodulateand decode a third modulated signal frame, wherein the third modulatedsignal frame comprises a difference between the first modulated signalframe and the second modulated signal frame to obtain a second part ofthe message; and controlling the demodulator, the decoder, the encoderand the modulator to demodulate and decode, encode and modulate, anddemodulate and decode a number of times based on the controlinformation.
 17. The system according to claim 16, wherein the processoris further configured to: determine whether each part included in the atleast two parts of the message has an error; if none of the parts of themessage is determined to have an error, combine the at least two partsof the message based on the control information to produce a combinationresult; and transmit the combination result to an application layer. 18.The system according to claim 16, wherein the processor is configured toobtain the control information for the message based on a typeassociated with the message and a configuration file listing out variousmessage types and control information corresponding to the variousmessage types.
 19. A method for extracting a message from a receivedsignal frame, comprising: receiving a signal frame having N parts thatare modulated with different power levels, where N is an integer equalto or greater than 2; demodulating and decoding the received signalframe to obtain N bit sequences that correspond to the N partsrespectively; and forming a message based on the N bit sequences and apartition scheme, wherein the message is partitioned into N messageparts corresponding to the N bit sequences respectively according to thepartition scheme.